98 X 2" TT/Shackles 31's

[Kinnish]

Wow, So many thoughts about whether or not I should do the torsion twist and shackles on my X so I can make room for 31BFG's and MT Classic 2's. My first concern is power, with this new setup I'm sure to loose power, but how much is the question, I have the SOHC. If I were to chip it and add intake and exhaust would I make up for this lose? My current gearing is 3.43 and it seems terribly expensive to change this to 3.73. A buddy of mine said a mechanic told him it would cost close to a $1000 to do this task, but then agin this seems rather high to me. Pleeez, all opinions welcome!!! Hopefully I can order this stuff soon or just get it outta my head ....


PS: With the lift and new tires how much in estimation would my gas mileage drop ( currently 14-16mpg)?

 

[jobunn]

I have a '99 Sport 4x4 with the TT, Shackles and 31x10.5 BFG A/T. My mileage dropped about 30 miles per tank or roughly a mile and a half per gallon. Not too bad....it was worth it.

As far as power, I have noticed a little difference off the line, little difference other than that. I would imagine a chip and exhaust would put you back to par.

 

[Robert]

Jobunn, yours is a 4x4 which should have lower gears than the 3.43 in Kinnish's Explorer. With 3.43 gears, I would have to believe his is a 2WD. I can't imagine Ford putting them in a 4x4, but you never know. 3.43 with 31" tires will definately be felt. My '97 4x4 with SOHC came stock with 30" tires and a 4.10. I now have 32" tires which still amounts to an overall ratio that Ford offered. It is the equivallent to having 3.73s with 235 75R15 tires. It is fine for power and my mileage never changed. I did feel the drop in low end power though. I would never consider running 31" tires with a 3.43, but maybe I am more picky than most people. I would prefer to have a little better pickup off the line and sacrifice some mileage.

That said, Kinnish if you do have a 2WD then you can get it regeared for $400-$500. The $1000 price should be for front and rear.

 

[Alec]

I had the stock 3.27s when I put my 31's on and decided to throw in 3.73s. My mileage dropped about 1 mpg with the lift, but the "yee-haw!" factor soared way above that

With intake and exhaust, it'll even out to what you felt before. However, there's always room for more power!

 

[justin146]

I have 33's and I haven't noticed any change in gas mileage. It is kinda hard to figure out gas mileage after you put on tallet tires. If you do the math using your odometer, you will come out with a lower number of miles per gallon--BUT you are travelling farther that your odometer indicates meaning you are getting better gas mileage than you think. ALL of this is true unless you have corrected your speedometer.

I have noticed a slight loss in power but my gas mileage has remained the same. I guess the taller tires gear me to make up for the rolling resistance of the wider tire and unsprung weight.

I went from a 255/70/16 to a 285/75/16 which is basically going from a 30x10?? to a 33x11.5.

 

[Robert]

justin146 -- multiply your odometer by 1.092 to get the true miles driven if you haven't adjusted your speedometer to account for the taller tires. Divide your answer by the number of gallons it took to fill up and you will have your actual MPG.

 

[Kinnish]

Just checked my axle code : 45 - 3200 "3.55" gearing on it. So now how will gearing affect me with 31's and rims?

 

[Alec]

Effectively, your gear ratio will be around 3.27 (for a number we all know and love) after the tires with your current gears. 3.27 is the factory ratio I had and I was fine with it most of the time. You get great mileage, but low-end grunt leaves a bit to be desired. All in all it's livable, but if you do a lot of wheeling might be a bit annoying; though you can always pop it into 4lo if you need more grunt. With only 2wd, I can't.

Basically you'll be fine for now, but if you ever want to go bigger you'll need new gears.